Evolution of Mobile Services
Mobile phone services and technologies have evolved rapidly, as has the global market for mobile phones, including significant cycles of boom and bust. Basic mobile network technologies have evolved from 'plain old' GSM through GSM Phase 2+, otherwise known as 2.5G (GSM, GPRS, EDGE), to UMTS 3G, with similar evolutions from CDMA to 3G CDMA2000. Symbian OS has tracked these evolutions. It enables control of landline and mobile phone modems and supports wireless telephony standards for all markets.
GSM uses a packetized but synchronous Time-Division Multiple Access (TDMA) approach to sharing available bandwidth between multiple users. Voice is digitally encoded and transmitted as digital packets in timeslots (frames) at a data rate approximating 19 200 baud (equivalent to modem speeds from around the late 1980s).
Support for basic GSM services requires support for receiving and making voice calls, receiving and sending SMS messages, showing that SMS messages have been received, and receiving and making circuit-switched data calls, for example fax calls. GPRS adds the requirement to support making and receiving packet-switched data calls.
EDGE and 3G networks extend these requirements to include, for example, both one-way and two-way audio and video calls including support for two-way tele-conferencing; streaming of audio and video to a phone; interactive, session-like two-way request-response (for web browsing or remote database query); and background data delivery for example of SMS messages.
GPRS and EDGE add packet data services by stitching together multiple GSM voice channels to create a higher bandwidth channel. GPRS provides data rates up to 170 kbps, which EDGE improves by a factor of three (either in speed or in the number of simultaneous subscribers supported at GPRS data rates).
Both GSM and CDMA remain circuit-oriented, voice-centric technologies. UMTS evolves GSM to use Wideband CDMA to gain higher data rates. Unlike GSM or CDMA, UMTS is fully packet-switched, not circuit-switched.
Historically, CDMA has dominated the North American market, while GSM originated as a European standard that has had widespread global uptake. GSM has also recently increased its market share in many CDMAdominated markets to become a second-line network technology.
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